Fig. 2. Detection of the RB gene using the RB-specific PCR marker in plasmids or plants (transgenic Katahdin lines or backcrossed progenies derived from potato x Solanum bulbocastanum somatic hybrids) that are known to either have or not have the RB gene. Lane 1, potato cultivar Katahdin; Lane 6, negative control without template DNA; Lane 22, S. bulbocastanum clone PT29; Lanes 2, 7, 12, 25, 27, plasmids containing RGA1, RGA4, rb, RB, RGA3, respectively; Lane 3, 4, 11, 13, 17, 18, 21, 26, late blight–resistant transgenic Katahdin lines SP922, SP968, SP925, SP960, SP1006, SP1464, SP898, SP920, respectively; Lane 8, 9, 16, 19, 23, late blight–susceptible transgenic Katahdin lines SP937, SP941, SP991, SP947, SP953, respectively; Lane 5, 10, 15, 24, late blight–resistant BC1 clones J101A32, J101A45, J101A7, J101K6, respectively; Lane 14, 20, late blight–susceptible BC1 clones J101A39 and J101A20, respectively; Lane 28, late blight–resistant BC2 clone J101K6A22. A 213-bp band is amplified in all lanes that contain the RB gene.